Fetal motor activity has long been recognized as a good predictor of fetal wellbeing as discussed in Fetal Movements In utero—A Review, Sadovsky, E., M. D., Isr. J. Obstet. Gynecol. 1992: 3:27-36. Different types of fetal motor activity are discussed in an article entitled “Classification of human fetal movement” by Ilan Timor-Tritsch, et al., AM. J. Obstet. Gynecol., Volume 126, Number 1, pages 70-77, the contents of which are incorporated herein by reference. Exemplary fetal motor activity includes strong fetal kicks lasting from about ½ sec to about 1 sec, weak fetal punches lasting upto about ½ sec, and long fetal rolls lasting from about 10 sec to about 15 sec.
Commonly owned PCT/IL2003/000609 entitled Bio-filter Pad for Facilitating the Detection of an Occurrence of a Physiological Action, and Method Therefor, and Fetal Activity Monitoring Apparatus published under PCT International Publication No. WO 2004/012598 illustrates and describes fetal motor activity monitoring systems suitable for home use for providing information regarding fetal wellbeing based on detecting an expectant mother's abdominal movements as a consequence of fetal motor activity. WO 2004/012598's FIG. 1 shows a fetal motor activity monitoring system 1 including a bio-filter pad 2 adapted for removable intimate adhesion to an expectant mother's abdomen, and having a moving coil transducer 3 centrally disposed thereon for sensing her abdominal movements for providing a visual indication regarding a prevailing level of fetal motor activity. The transducer 3 is connected to a credit-card like, battery powered, fetal motor activity recorder 4 having an amplifier 6, an A/D converter 7, a signal processor 8, a memory 9, an output interface 11, for example, RS-232, and a fetal motor activity display 12 for comparing the prevailing fetal motor activity during a fetal motor activity monitoring session to a regular level of fetal motor activity determined on the basis of historical information. The fetal motor activity recorder 4 may be integrally formed with a transducer 3 together constituting fetal motor activity monitoring apparatus (see WO 2004/012598's page 5, lines 29-30). WO 2004/012598's FIG. 6 shows a fetal motor activity monitoring system 31 similar to the fetal motor activity monitoring system 1 except implemented for telemedicine purposes.
U.S. Pat. No. 4,898,179 to Sirota illustrates and describes a device for detecting, monitoring, displaying and recording of the heartbeats of a pregnant woman and her fetus. In addition, a third sensor can detect movement of the fetus and activate a display of a moving infant or a numerical display of the movement intensity or frequency.
U.S. Pat. No. 5,140,992 to Zuckerwar et al. illustrates and describes an ambulatory passive sensor for use in a fetal motor activity monitoring system. The passive sensor includes a piezoelectric polymer film combined with a metallic mounting plate fastened to a belt and electrically connected to a signal processing unit by means of a shielded cable. The sensor receives pressure pulses emitted from a fetus inside an expectant mother and has means for filtering out pressure pulses arising from other sources such as the maternal heart. The belt is resistant to stretching such that any pressure pulses cause compression of the piezoelectric polymer film thereby affecting its net polarization to produce detectable voltage changes.